Study And Design Of Receive-only Phased Array RF Coils In Open MRI System

Open magnetic resonance image (MRI) system has been widely studied and used because of its low cost, convenient maintenance, ample imaging space, and available access to operate. However, the advancement on open MRI system has mainly been concerned at improving the magnet and little work has been dedicated to the radiofrequency coil. While radiofrequency coil, as a primary component in MRI systems, determines the image quality. Therefore, this dissertation focuses on phased array receive coil in open MRI systems, and the mainly two parts of this study are as follows:First of all, a method for designing the construction of phased array coils was presented, and it was used for designing a 4-channel receive PA knee coil. We studied the angle between the RF field generated by the coil element center and the main magnetic field,the width value of the coil and their impact on the performance of the whole phased array coil system. The above parameters was optimized by simulation software. According to the results, a prototype 4-channel receive PA knee coil was constructed in an open MRI system and trialed in MRI studies on a phantom and human knee. The SNR of acquired phantom images is 78, the uniformity of acquired phantom images is 78.2%, and the human knee images further demonstrated the feasibility of the proposed method.Secondly, a two-channel phased array coil is adopted to substitute the surface coil in quadrature shoulder coil, optimizing the structure of quadrature shoulder coil. Hense, a three channel shoulder coil was designed and constructed. The simulation experiment and the phantom imaging experiments verified the feasibility of this method and evaluated the performance of the created prototype coil. Compared with quadrature shoulder coil, the result demonstrated that the SNR of the optimized three channel shoulder coil improved by 19.8% on the premise of keeping the uniformity.